Browsing IJAFR, volume 44, 2005 by Subject "Genotype"
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Effect of suckler cow genotype on cow serum immunoglobulin (Ig) levels, colostrum yield, composition and Ig concentration and subsequent immune status of their progenySurvival of the neonatal calf is largely dependent on humoral immunity. The objective of three experiments reported here was to compare cow serum immunoglobulin (Ig) concentration, colostrum yield, composition and Ig concentration and calf serum Ig concentrations at ~8- and 48-h post partum of spring-calving Charolais (C) and Beef × Holstein-Friesian (BF) cows and their progeny. Cows were individually offered a restricted allowance of grass silage pre partum in Experiments 1 and 2 and silage ad libitum in Experiment 3. In Experiment 1 calves were assisted to suckle after parturition. In Experiments 2 and 3, colostrum yield and Ig concentration were measured following administration of oxytocin and hand milking of half or the complete udder, respectively. It was intended to feed each calf 50 ml (Experiment 2) or 40 ml (Experiment 3) of colostrum per 1 kg birth weight via stomach tube. Following an 8-h period, during which suckling was prevented, a further colostrum sample was obtained. The decrease in cow serum IgG1 concentration pre partum was greater (P < 0.05) in BF cows than C cows. In comparison to BF cows, C cows had a lower colostrum yield (P < 0.001) and the colostrum had lower concentrations of dry matter (P < 0.01), crude protein (P < 0.05), fat (P < 0.05), IgG1 (P = 0.06), IgG2 (P < 0.01), IgM (P < 0.01) and Ig total (P < 0.05). The mass of IgG1, IgG2, IgM, IgA and Ig total in the colostrum produced was significantly lower for C cows than BF cows. Calves from C cows had significantly lower serum Ig subclass concentration at 48-h post partum than calves from BF cows. In conclusion, due to a lower Ig mass produced by their dams, calves from C cows had a lower humoral immune status than those from BF cows
Effect of suckler cow genotype on energy requirements and performance in winter and subsequently at pastureThree experiments using a total of 62 Charolais (C) and 110 Beef × Holstein-Friesian (BF) spring-calving cows were carried out to determine the relative energy requirements of the genotypes. Cows were individually offered a restricted allowance of grass silage daily during the last 85 and 107 days pre partum in Experiments 1 and 2, respectively, and ad libitum grass silage during the last 93 days pre partum in Experiment 3. In all 3 experiments grass silage was offered ad libitum during the first 34 days of lactation. In Experiments 1 and 2, cows and calves were grazed together during the subsequent grazing seasons. When fed to appetite, silage dry matter intake was similar for both cow genotypes but was higher for the BF cows when expressed relative to live weight. For Experiments 1 and 2 combined, initial live weights and live weight changes to post-partum, over the indoor period and at pasture were 720 (s.e. 14.1), 613 (s.e. 8.4), –74 (s.e. 4.0), –63 (s.e. 2.7), –106 (s.e. 6.0), –89 (s.e. 4.0) and 120 (s.e. 7.0), 88 (s.e. 5.3) kg for C and BF cows, respectively. In Experiment 3 the corresponding initial live weights and live weight changes to post partum were 759 (s.e. 12.3), 659 (s.e. 9.1) and –63 (s.e. 4.9) and –52 (s.e. 3.5) kg. There was no effect of genotype on body condition score or adipose cell diameter or their changes. Plasma creatinine concentrations were higher (P < 0.001) in C cows than BF cows. It is concluded that the energy requirements of a 660 kg C cow are approximately equivalent to a 600 kg BF cow during late pregnancy.
Effect of suckler cow genotype on milk yield and pre-weaning calf performanceMilk yield and pre-weaning calf performance of spring-calving Charolais (C) and Beef × Holstein-Friesian (BF) cows was compared over 3 experiments. Cows were individually offered a restricted allowance of grass silage pre partum in Experiments 1 and 2 and ad libitum silage in Experiment 3. In all three experiments cows received silage to appetite for the first 34 (s.d. 16.2) days of lactation. In Experiments 1 and 2, cows and calves were grazed together during the subsequent grazing seasons. The daily milk yield of C cows was significantly lower from parturition until turnout to pasture (1.8 to 2.5 kg/day lower) and subsequently at pasture (4.5 and 3.1 kg/day lower in Experiments 1 and 2, respectively) than that of BF cows. Calves from C cows consumed more (P <0.01) concentrate creep feed during the indoor period than calves from BF cows. Compared to calves from BF cows, pre-weaning daily live-weight gain was lower for calves from C cows in Experiments 1 (P < 0.05) and 2 (P = 0.06). The pre-weaning growth response per 1 kg increase in milk yield was greater for calves from C cows than those from BF cows. In conclusion, compared to BF cows the milk yield of C cows was lower resulting in increased calf concentrate intake indoors and lower pre-weaning calf daily live-weight gains.